Maybe you’ve seen a little story today about mercury, pregnancy, fish, and attention-deficit/hyperactivity disorder (ADHD). If you haven’t, you probably will. The news release headline says, “Prenatal mercury exposure may be associated with risk of ADHD-related behaviors.” The modifiers in there “may be” and “related” won’t stop the mental math from this study translating as “pregnant+mercury=ADHD,” and it won’t stop headlines from implying as much. Mix in a confusing finding about eating fish during pregnancy–protective or harmful?–and what’s a science consumer to do?

The study relied on a cohort of children born from 1993 to 1998 and their mothers. About 10 days after each mother gave birth, she filled out a questionnaire about what she’d eaten during pregnancy–including fish broken down by category–and gave up a hair sample. Investigators at Brigham and Women’s Hospital in Boston evaluated the hair for levels of methylmercury, an organic form of mercury that the central nervous system readily takes up. When the children reached the age of 8, they underwent testing that evaluated behaviors related to ADHD. The study was originally designed to assess the relationship, if any, between exposure to polychlorinated biphenyls contaminating a local harbor and neurodevelopment.

According to the findings, ADHD-related behaviors in the 607 evaluated 8-year-olds increased with increasing methylmercury values from mom’s hair around the time she gave birth. These associations were stronger for boys than girls for some features, with a slightly increased risk for ADHD-related behaviors above a mercury value of 1 microgram/gram in the hair. But fish consumption during pregnancy was linked to reduced levels of ADHD-related behaviors in the children.

Pregnancy and fish

What’s a pregnant woman to do, given that a lot of fish we’d like to eat contain a lot of mercury? “Fish is the predominant source of mercury intake for pregnant women,” says Bruce Lanphear, who wrote a commentary accompanying the study, both published in Archives of Pediatrics and Adolescent Medicine. That information, he adds, “shouldn’t change the recommendations to pregnant women about eating fish that is low in mercury.” Which fish are which? Here’s a handy guide, but briefly, salmon, trout, and catfish tend to be low mercury while shark, tuna, and mackerel (sob!) are no-nos.

So, first take-home is, you can keep eating fish. Just don’t eat fish that have a lot of mercury in them. Nothing’s changed there. In fact, eating fish without a lot of mercury seems to be protective, so get thee to a good fish market and pick something tasty, low-mercury, and sustainable for dinner. What we need here is a sustainable × low-mercury guide to make all of this easier.

ADHD and mercury

But what about this ADHD and mercury link? Well, this study doesn’t actually report a link between mercury and ADHD. As study senior author Susan Korrick, assistant professor of medicine at Brigham and Women’s Hospital in Boston, notes, “it’s really important to keep in mind that we did not look clinically at children diagnosed with ADHD.” This cohort was just a general population of children tracked after being born healthy and vaginally, and as with any children, no one knew when they were born how they’d turn out. So some might have ADHD, but overall, they simply represent a general population. “We were looking at behaviors largely across the normal range, which is very different from looking at a clinical diagnosis of ADHD,” Korrick says. “It’s beyond the scope of this research to make inferences about clinical ADHD.” ADHD has a large inherited component [PDF], so if your child has ADHD, you don’t need to waste hours guiltily assessing your fish intake during pregnancy.

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“A much lower brain concentration of total Hg was observed in the thimerosal monkeys compared with the MeHg monkeys, that is, a 3- to 4-fold difference for an equivalent exposure of Hg”

So, actually less mercury was found from ethyl mercury (thimerosal) exposed animals than methyl mercury.

“Methylmercury is tighly bound to tissue in fish and some is defecated out of the body.”

Mercury from ethyl mercury (thimerosal) is exctreted in the feces as well. Pinchichero’s work demonstrated that clearly. One does wonder why you left that detail out. Makes ethyl mercury sound much more scary.

“Ethylmercury is injected into infants muscle whose main purpose is to provide rapid access to the bloodstream.”

Not correct. The main purpose of the ethyl mercury (thimerosal) was to prevent organic contaminants from multiplying in a vaccine vial. A multidose vaccine has the chance to introduce contaminants.

I’ll take accurate information any time. Which is why I read articles by people like Dr. Willingham and double check anything written by people who leave comments on web-based articles. Like I did above. Glad I did as there was a lot of incorrect information in your comment.

“Hg++ is the toxic agent in brains. Ethylmercury deposits 5 times as much Hg++ in the brain as equal doses of ingested methylmercury”

This is not accurate. Since ethyl mercury is broken down faster than methyl mercury, one can find more elemental mercury (inorganic mercury) if one measures soon after exposure. Total mercury in the brain is higher with methyl mercury and, long term, this will result in larger concentrations of inorganic mercury as the methyl mercury is broken down.

“Methylmercury is tighly bound to tissue in fish and some is defecated out of the body.”

Ethyl mercury is also excreted in the feces. Did you not know this? If you didn’t, why didn’t you look it up before writing? If you did, why didn’t you include it in the above statement? As written, the above statement is misleading. It makes a reader think that mercury from ethyl mercury exposure is not excreted at all, which would raise the fear factor.

The dose time product is higher from ethylmercury. The remaining mercury level at the end of the experiment is higher. The half life is so long that it can not be determined in this experiment. Please stop trying to confuse the issue.

“The sales promotion men, for their part, were kept busy mounting a front against the doctor and the pharmacist. One salesman wrote, “my happy laughter at appropriate references to the completely harmless properties of the drug were apparently successful in putting the often anxious pharmacists minds at rest.’

After a visit to a university neurological clinic in Cologne to defend Contergan (Thalidomide), Dr. Goeden of Chemie Grunenthal stated in a letter of February 23, 1961 that “I declared our standpoint on the problem of polyneuritis and Contergan and sought above all to cause confusion.” Thalidomide and the Power of the Drug Companies, Sjostrom and Nissen, 1972, pp. 61-62.

Matt Cary-Sullivan-LeftBrainRightBrain or whatever name name you are going by today, you have zero qualifications concerning the toxicokinetics of mercury. You are a developmentally disabled, unemployed adult blogger who thinks they are autistic. You need to go back to your own blog. We are not your cronies here. I did not say the purpose of thimerosal is to provide rapid access to the bloodstream. I said the purpose of intramuscular injection is to provide rapid access to the bloodstream. You adults who claim to be autistic have nothing in common with a vaccine injured child. Go get a job or something.

I have never claimed to be developmentally disabled. I am employed. I don’t think I am autistic.

My child is autistic. Because of that I have spent a great deal of time taking a look at the evidence behind many claims made about autism. I have spent a lot of time looking at claims about mercury and autism. What I have found is that there is no substance to those claims. The claims you and others have repeated on this discussion are good examples of these sorts of claims.

I make no claims to being an expert in toxicokinetics. Do you? If so, what are those credentials?

I am, however, a researcher with over 25 years in materials synthesis and charactrization.

I do not believe the “you are not like my child” comments which are used to brush aside comments from adult autistics contribute to a good discussion.

My last name is spelled with an “e”. Carey. Nothing hidden about my name.

I have never claimed to be developmentally disabled in general nor autistic in specific.

I am employed and have never represented myself otherwise.

My career is as a researcher in materials synthesis and characterization. I have never presented myself as an expert in the toxicokinetics of mercury. Are you claiming that you are? If so, how do you explain your multiple mistakes?

You are correct on one count, I am an adult. I do write. Not as well as Dr. Willingham, but I try. I try to undo the misinformation that pervades the online discussion of autism.